1. Field of the Invention
This invention relates to a controller, and more particularly to an improved device such as a programmable controller suitable for a sequence control.
2. Discussion of the Related Art
There is well known a controller or a sequence control system employing a programmable controller, in which a communication unit as a master station is mounted to a base unit of the programmable controller, terminals as a plurality of slave stations are connected to the communication unit, and each of the terminals is connected by an input unit such as a limit switch or various sensor or an output unit such as a air valve or an actuator. In such a well known sequence control system, ON-OFF input data produced from the input unit such as the limit switch or various sensor is transferred to the programmable controller through the terminals, the programmable controller receives the input data to operate the received data in accordance with a program set beforehand and generate ON-OFF output data to be applied to the output unit such as the air valve or actuator through the terminals, and a machine tool is thus controlled.
The conventional programmable controller is provided with a connector connection unit to be connected with a programming tool, RS232 association components device or the like. When a cable connector of the programming tool is mounted on the connector connection unit, the cable connector is kept to externally project from a main housing body of the programmable controller. That is, the cable connector mounted on the main housing body of about rectangular parallelepiped is kept to eternally project bringing a dead space by the wiring. In the sequence control system, the base unit of the programmable controller is mounted by the communication unit employing a communication CPU whereby an input-and-output response time is delayed because data transmission is delayed between the CPU of the base unit and the communication CPU of the communication unit. The base unit of the programmable controller and the communication unit are separated units, so that an interface circuit or the like is necessary to be disposed between the both units and each unit has to be provided with CPU, resulting into a bulky configuration and expensive controller.
It is, therefore, a primary object of this invention to provide an improved controller in which a dead space for wiring is decreased, an input-and-output response time is shortened, its configuration is miniaturized, and its manufacturing cost is reduced.
According to a first aspect of this invention, there is provided a controller including a connector connection unit for connection with a cable connector, a housing having difference in level and a display disposed on a higher level section of the housing, one board disposed in parallel with a side wall of the housing, another board disposed to cross the one board, the one board being positioned on the higher level section of the housing and the connector unit on the another board being positioned on a lower level section of the housing. The difference in level corresponds to height of a connector connected with the connector connection unit. The another board is provided with a power supply circuit and the one board is provided with a control circuit.
Since the connector connection unit is placed on the lower level section of the main body housing, the controller may easily ensure wiring space by avoiding such conventional inconvenience that a cable connector projects from the main body housing of the controller. The one board is positioned in parallel with the side wall of the housing and the another board is placed to cross the one board so that they may be effectively accommodated by the housing having the lower and higher sections, resulting into miniaturization of the controller. The control circuit mounted on the one board is separated from the another board provided with the power supply circuit, so that the control circuit is free from heat or noise from the power supply circuit and the freedom of mounting design of the boards is improved.
According to a second aspect of this invention, the controller receives input data from an input unit through a terminal and produces output data to be applied to an output unit through the terminal, and further includes a communication means for executing a serial communication with the terminal to receive and send the input and output data. The controller including the communication means for receiving and transmitting the input and output data about the terminal by serial communication does not need any communication unit which is conventionally necessary as a master station, so that data transmission speed of this controller is higher than that of the conventional controller employing the communication unit existing in the communication.
According to a modification of the second aspect of this invention, there is provided a programmable controller further including a control means for repeatedly executing an input process for reading input data received by the communication means, an output process for sending output data to be transmitted to the communication means, a program execution process for executing a user program, and other process, the program execution process being executed between the input process and its subsequent output process, and the other process being executed between the output process and its subsequent input process. The communication means starts in response to the output operation. One communication cycle of the communication means starts by transmission of the output data and ends by receipt of the input data following the transmission.